Multi-contact plug and socket assemblies are well known and commonly used, particularly for connecting a first group of electrical leads or wires to a corresponding large group of leads or wires, for example in multi-conductor connectors for use in digital systems.
When the number of plug and socket contacts becomes very large, e.g. of the order of 100 or more as an example, the force required to assemble and disassemble the connector can become quite high, e.g. 15 pounds or more, and this not only makes such connecting and disconnecting difficult for the
One system which has been proposed to alleviate this problem uses a so-called jack-screw, mounted near the middle of the connector, with which the aligned contacts of plug and socket can be drawn together by turning of a screw extending between them. However, this construction is relatively expensive, and requires a substantial screwdriver operation to assemble and disassemble the connectors.
Another type of system has been proposed which requires no jack-screw, because only a very small force is needed to assemble and disassemble the plug and socket from each other. This system utilizes a plurality of so-called receptacle contacts. Each receptacle contact comprises a shell with enclosing sidewalls, and is open at least at one end. From the open end, at least one and preferably three resilient cantilevered contact beams extend obliquely within the shell; preferably also, the three beams comprise a central beam and two outboard beams, one on each side of the central beam. The resilient central beam extends obliquely within the shell from a first shell wall at the open end of the shell, toward the interior side of a second, opposite shell wall. More particularly, this central beam is biased by its own spring characteristic toward a position in which a free distal end portion thereof lies adjacent to the second shell wall. The two resilient outboard beams, one on each side of the central beam, extend obliquely within the shell from the open end of the second, opposite shell wall toward the first shell wall, and each is biased by its own spring characteristic toward a position in which a free distal end portion thereof lies adjacent to the first shell wall.
With this beam configuration, a blade contact can easily, and with minimal force, be inserted into the open end of the shell and advanced until the distal end portion of the central beam lies against one side of the inserted blade, and the distal portions of two outboard beams lie against the other side of the blade, thereby providing the desired contact between blade and beams.
In order to provide good, long-lived electrical contact between each beam and its corresponding inserted blade, a contact with a surface of a noble metal, such as gold, is preferably provided at the point on each beam where it contacts the corresponding blade. This can be done by coating the entire receptacle contact with a noble metal, such as gold, but this is expensive; however, it has not been feasible to coat just the distal tip of the beam with a noble metal, since it is inside the receptacle shell.
It has also been proposed to make the receptacle contact by bending up the shell and beams from a flat blank of resilient metal. This opens up the possibility of applying a localized deposit of noble metal on the distal end portions of the beams before the blank is bent up, and while they are accordingly exposed. However, if this is done, the mechanical manufacturing steps of stamping out the blank and bending it up into the form of a receptacle contact, with the cantilevered beams inside it must be interrupted after the stamping step so that a separate, localized plating process can be performed, and the locally plated blank must then be returned to mechanical processing. Not only does this introduce delay and inconvenience into the fabrication process, but it also requires special care in the mechanical processing so that the local noble-metal deposit is not injured during the rest of the mechanical processing.
It is an object of this invention to provide a receptacle contact for mating with a blade-type contact which requires only a small force for assembly and disassembly of the connector, and is relatively inexpensive to manufacture; it is also an object to provide a simple and inexpensive method of making such a receptacle contact.